A lighting system typically includes an electronic converter 10 and at least one lighting module 20.
For example, the electronic converter 10 may include an AC/DC or DC/DC switching supply, receiving at input a supply signal (e.g. from the mains or from a battery) and providing at output a regulated voltage Vout or a regulated current iout.
A lighting module 20 includes one or more light radiation sources including e.g. at least one LED (Light Emitting Diode) or other solid-state lighting means such as e.g. laser diodes.
For example, FIG. 1 shows a system wherein the electronic converter is a voltage generator 10V and similarly the lighting modules 20 are modules 20V configured to be supplied with a voltage. For example, FIG. 1 shows two lighting modules 20V1 and 20V2.
Therefore, in FIG. 1, the electronic converter 10V provides at output, via a positive terminal 100a and a negative terminal 100b, which represents a ground GND, a regulated voltage Vout.
For example, FIG. 2 shows an example of a lighting module 20V configured to be supplied with a regulated voltage Vout.
Specifically, lighting module 20V1 includes a positive input terminal 200a and a negative input terminal 200b, for the connection to the terminals 100a and 100b of electronic converter 10V. For example, lighting module 20V may be connected, via a cable C1, to the electronic converter 10V. Therefore, terminal 200a is connected to terminal 100a, and terminal 200b is connected to terminal 100b, and therefore the lighting module 20 receives the voltage Vout.
In the presently considered example, the lighting module 20V is a LED module including one or more LEDs L connected between the terminals 200a and 200b. For example, module 20V may include a LED chain or string 22, wherein a plurality of LEDs is connected in series. Moreover, the LEDs L may also be distributed onto various branches connected in parallel. For example, as shown in FIG. 2, module 20V may include a first LED string 22a including a first set of LEDs connected in series, and a second LED string 22b including a second set of LEDs L connected in series.
As the lighting module 20V is supplied with a voltage, the lighting module 20 includes a current regulator 24 connected in series with each LED string 22. For example, in FIG. 2, the first LED string 22a and a first current regulator 24 are connected (e.g. directly) in series between the terminals 200a and 200b, and the second LED string 22b and a second current regulator 24 are connected (e.g. directly) in series between the terminals 200a and 200b. 
Therefore, in the presently considered example, the strings 22a and 22b are supplied with a common voltage (Vout). In this case, the LED strings 22 with the respective current regulators 24 included in the various lighting modules 20V should be connected in parallel at the voltage Vout provided by the electronic converter 10V. As a consequence, also the lighting modules 20V should be electrically connected in parallel to voltage Vout.
For example, in FIGS. 1 and 2, the lighting module 20V1 also includes a positive output terminal 200c and a negative output terminal 200d, for the connection to a following lighting module, for example module 20V2. Specifically, said terminals 200c/200d are connected (e.g. directly) to the terminals 200a/200b. Therefore, the voltage (Vout) received at the terminals 200a and 200b is also applied to the terminals 200c and 200d. 
Therefore, the terminals 200a and 200b of the lighting module 20V2 may be connected (directly or via a cable C2) to the terminals 100a and 100b of the electronic converter 10V, or to the terminals 200c and 200d of the lighting module 20V1, which again provide the voltage Vout. As a consequence, although modules 20V1 and 20V2 are connected in series from a mechanical point of view, the electric connection is in parallel.
In the simplest instance, the current regulator 24 may be a resistor or a linear current regulator. The current regulator 24 may also be implemented by means of current mirrors or a switched mode current source regulator, typically including an inductor and an electronic switch.
On the other hand, FIG. 3 shows a system wherein the electronic converter is a current generator 10C, and similarly the lighting modules 20 are modules 20C configured to be supplied with a current. For example, FIG. 3 shows two lighting modules 20C1 and 20C2.
Therefore, in FIG. 3, the electronic converter 10C provides at output via the positive terminal 100a and the negative terminal 100b, which again represents a ground GND, a regulated current iout.
With a regulated current, the LEDs L distributed throughout the various lighting modules 20 are connected in series between the terminals 100a and 100b. 
Generally speaking, also in this case, each lighting module 20C includes two terminals 200a and 200b. For example, if only one single lighting module 20C may be connected to the electronic converter 10C, the LEDs L of said module are connected in series between the terminals 200a and 200b. 
On the other hand, in FIG. 3, a plurality of lighting modules 20C may be connected to converter 10C. In this case, each lighting module 20C moreover includes two terminals 200c and 200d for the connection to the terminals 200a and 200b of a following lighting module 20C. In this case, the terminals 200c and 200d of the last lighting module 20C, for example module 20C2, are short-circuited (internally or externally) to close the current path. As regards such a connection, mention may be made of document EP 2 805 101, the content whereof is incorporated herein by way of reference.
In this case, as shown in FIG. 4, the LEDs L of each lighting module 20C may be connected in series between the terminals 200a and 200c and/or between the terminals 200d and 200b. 
For example, in the presently considered embodiments, two LED strings 22a and 22b are connected in series between the terminals 200a and 200c, and terminal 200d is connected (e.g. directly) to terminal 200b. 
Generally speaking, also in this case, a plurality of LED strings may be connected in parallel, optionally having a resistor connected in series in order to improve the current distribution among the various strings. The person skilled in the art will appreciate that this solution is rather basic, because if LED strings are added or removed it is necessary to adapt the current provided by the electronic converter.
Therefore, the lighting modules 20 have a structure which changes as a function of the envisaged supply (voltage or current supply). Moreover, according to the needs, each lighting module 20 may include a different number of LEDs.
Consequently, in order to improve the characteristics of a lighting module 20, in particular as regards efficiency, light emission and LED pitch, the lighting module 20 must be designed specifically. For example, the designer must choose the correct LEDs, e.g. as regards spectral characteristic (colour) and brightness, and he must design a rigid or a flexible printed circuit board. While designing said printed circuit board, the designer must also take into account the electric configuration of the circuit (current or voltage driving) and the sizing specifications of the printed circuit board.
Therefore, these parameters must be taken into account each time the requirements vary, leading to the need of developing a different lighting module for each new application. As a consequence, also the designed printed circuit boards will be different from each other, which increases the manufacturing and storage cost of the printed circuit boards.    a. However, solutions are known which enable a partial re-use of the printed circuit boards of other products. For example, with reference to FIG. 2, the LEDs L of a module 20V may easily be replaced with LEDs of a different colour. Moreover, the brightness of module 20V may be varied, by modifying the current flowing through the LED string 22, e.g. by adapting current regulator 24 e.g. by modifying the reference resistor of a corresponding current regulator.
Also the lighting modules 20C with current supply may be re-used. For example, document EP 2 805 101 A1 shows LED modules which may be cut to different lengths. However, in case of a change of the supply current for the lighting modules 20C, the electronic converter 10C must be adapted.